Yams (Dioscorea spp.) in shellmounds and swiddens: ancient history in Babitonga Bay, Santa Catarina State, southern Brazil

Background In Babitonga Bay, southern Brazil, records of yam consumption exist among shellmound builders from at least 4000 years ago. Shellmounds (sambaquis) are anthropogenic structures in the form of mounds with layers of shells associated with other faunal remains, as well as with charcoal, artefacts and burial. Larger sambaquis are considered to be funerary monuments. The indigenous Jê and Guarani people also lived in the region before the European invasion and cultivated yams. Currently, exotic and domesticated yams are cultivated in the region by farmers. Our aim is to describe the long-term history between the people and Dioscorea in the Babitonga Bay region based on its consumption and occurrence in shellmounds and swiddens. Methods Surveys of Dioscorea spp. and host were carried out in the vegetation of shellmounds and in the surrounding area using visual detection through intensive searches in transects using the walking method. The survey of Dioscorea species used and cultivated in the precolonial, colonial and current periods was carried out based on the literature. In the present study, only Dioscorea trifida cultivations were recorded. Results Dioscorea cayennensis, Dioscorea chondrocarpa, Dioscorea dodecaneura, Dioscorea laxiflora, Dioscorea olfersiana, and Dioscorea scabra, all recorded in associated vegetation of shellmounds, in different combinations of the species. In swiddens, D. trifida is most common, followed by Dioscorea alata and, to a lesser extent, Dioscorea bulbifera and D. cayennensis. Records of food use prevail, but they are used as medicinal plants. Yams are integrated on anthropogenic soils of shellmounds and in swiddens in monoculture systems or in intercropping with Zea mays or Colocasia esculenta. The presence of exotic food trees and D. cayennensis in some shellmounds indicates the influence of colonizers on the composition of the vegetation. In sambaquis, there are overlapping processes of construction of cultural niches by different human groups at different times. Conclusions The sambaquis and the associated vegetation and swiddens form part of a domesticated landscape. The native species of Dioscorea recorded in shellmounds and surrounding vegetation do not depend on human action to perpetuate themselves in the environment. However, this does not rule out human influence in the past, but it does not indicate horticulture among the Sambaquianos. Greater investment in genetic, archaeobotanical and ethnobotanical research can contribute to a better understanding of the relationship between people and yams over thousands of years.

Shellmound builders (Sambaquianos) were fishermen [22] who lived and used plants from the ecosystems of the Atlantic Forest Biome [19,23] between the middle and late Holocene [24].Shellmounds (sambaquis) are anthropogenic structures [25,26] in the form of mounds with layers of shells associated with other faunal remains, as well as with charcoal, artefacts and burial [25].Larger sambaquis are considered to be funerary monuments [24], where feasts were held on the occasion of human burials [27].Shellmounds represent important records for understanding human influence on the coastal landscape of Brazil [28].Studying them provides an understanding of settlement patterns, the functions of sites, subsistence and social organization [25].The archaeological plant remains in shellmounds provide important indications of diet [29].Fragments of carbonized yam tubers from 6000 years BP (before present) have been recovered in the southeastern region [23].In the southern region, Dioscorea starch grains in the Morro do Ouro shellmound in Babitonga Bay date to 4030 ± 40 years BP [30,31] and those in Jabuticabeira shellmound date to 2880 ± 75-1805 ± 65 years BP, located in a lagoon complex [32,33].
Yams are among humans' oldest foods [34] and have been recorded in archaeological sites since the Pleistocene [35].These foods rich in carbohydrates and sources of bioactive substances for medicinal use [36][37][38] are important in tropical regions [39].
The domestication of Dioscorea likely started with forest management through the selection of yam plants and the protection and gathering of tubers [34].In tropical forests where perennial yam tubers are common, they provide a source of food for long periods [36,40].
Of the more than 640 existing species of Dioscorea (Dioscoreaceae) [41], twelve are widely cultivated today, with an emphasis on African and Asian species [38,42].The use of Dioscorea tubers in Brazil is still minor, with a predominance of exotic Dioscorea alata L. and D. cayennensis Lam., both introduced in the sixteenth century by Portuguese colonizers, and of Dioscorea bulbifera L., introduced by Dutch settlers [43].The Amazonian species D. trifida L.f., domesticated by indigenous people before European invasion, is currently cultivated mainly in northern, southern and southeastern Brazil [44,45].The consumption of native and wild yams in Brazil is linked to indigenous peoples and farmers, who use and cultivate them on a small scale [46,47].In Santa Catarina state, southern Brazil, the main yam-producing farmlands are located in the Babitonga Bay region [48].The tradition is currently maintained by descendants of European immigrants, who in the nineteenth century incorporated yam cultivation from their contact with colonizers and indigenous people [49,50].
Considering the ancient consumption of yam by Sambaquianos and the records of their intense and longterm interaction with the forest, are there species of Dioscorea among the vegetation today associated with these places that could have been consumed by them?How does the current consumption and cultivation of yam in the Babitonga Bay region relate to its ancient use by the native indigenous peoples who lived there, including the Sambaquianos?Thus, the objective of this study is to analyse the interactions of this long-term history between people and yams in Babitonga Bay and find current species of Dioscorea associated with different landscape units, especially concentrated in shellmounds and swiddens.

Study area
The study area is located in the municipality of Joinville, located on the northern coast of Santa Catarina state, southern Brazil (Fig. 1).The ecosystems in this region are part of the Atlantic Forest Biome, with a predominance of mangroves, Restinga forest, and Dense Ombrophilous Forest (FOD) distributed around Babitonga Bay [51].In Joinville, 41 shellmounds are registered [52], most of which are found around this estuary [53] (Fig. 1).According to the classification proposed by Köppen, Joinville is classified as having a mesothermal climate, as the temperatures in the coldest month are below 18 °C and above 3 °C and classified as humid, as it does not have a defined dry season [51].
Seven shellmounds were selected for the present study (Fig. 1; Table 1) based on the following criteria: location in the region of Babitonga Bay; presence of forest component in their surroundings; history of interventions in its structure and vegetation composition, such as the exploitation of shells for the production of lime and the carrying out of archaeological excavations.In addition, Morro do Ouro shellmound was included due to the identification of archaeobotanical material that attested to the consumption of Dioscorea sp.[31].

Dioscorea surveys
The surveys of Dioscorea spp.were carried out in the vegetation above the shellmounds and in the surrounding area.On the shellmounds, individuals of Dioscorea spp.and host were registered by walking [54] and wide patrolling methods [55].The vegetation in the shellmounds and surrounding areas was characterized based on the recording of tree species obtained using the walking method.Around the Cubatão I shellmound, the survey was stratified into two subareas, where CUB I-A is the portion with forest and CUB I-B is the portion covered by grasses and sparse tree vegetation.In the vegetation surrounding the shellmounds three transects, 20 m apart, are with up to 500 m in length from the edge of the site.Up to a distance of 5 m on both sides of each transect, visual detection of Dioscorea was performed [56] through intensive search by two or three observers [57].
In the sambaquis Morro do Amaral II, Rua Guaíra and Cubatão I, the surrounding forest is contiguous to their edges, while in the others, it starts at different distances from these structures.In the Lagoa Saguaçu shellmound, the forest starts beyond 100 m of a wide mangrove strip; The survey of Dioscorea species cultivated in the study area was based on data from previous research in the region by Santos [48], Veasey et al. [44], Siqueira [58] and Nascimento [59], who identified D. trifida as the main species cultivated.
In this research, we only recorded the cultivation of D. trifida in the rural area of Joinville, which is divided into two main regions: Pirabeiraba and Piraí, which have 8 and 14 roads, respectively, that provide access to rural properties.To record the cultivation of D. trifida, 10 km

Ancient consumption and cultivation of Dioscorea
The first record of Dioscorea consumption in the study area is 4030 ± 40 years BP by Sambaquianos, based on the identification of starch grains extracted from dental calculi in human remains recovered from Morro do Ouro shellmound [31].From the post-Sambaqui culture period (1000 years BP) to the period of contact with colonizers in the sixteenth century, there is little information in the literature about the plant resources used by the indigenous peoples of Jê and Guarani in Babitonga Bay.According to the literature, these two indigenous groups consumed Dioscorea tubers and cultivated plants in other regions of the state of Santa Catarina [62,63].
The oldest record of European contact in this region is by Binot Palmier de Goneville in 1504 [64].According to the account of this French explorer, he found the Guarani, then called Carijós, with dozens of villages where they cultivated cassava (Manihot esculenta Crantz) and other roots and tubers, probably sweet potato, Ipomoea batatas (L) Lam., and yams (Dioscorea spp.).The use of Dioscorea in Babitonga Bay appears in historical records only from the nineteenth century onwards, when there is mention of the cultivation of D. alata by Luso-Brazilian colonizers, when the naturalist Saint Hilaire visited Vila de São Francisco (currently São Francisco do Sul municipality) in 1820 [65].Another record is the cultivation of D. bulbifera reported by Theodor Rodowicz-Oswiecimsky in 1851 in the newly formed Colônia Dona Francisca [50], which today is the Joinville municipality.According to this visitor, the German colonizers learned to cultivate yams with the Luso-Brazilians and their slaves.
In this study, we recorded the cultivation of D. trifida in seven farmlands, one on Estrada dos Morros, in the Piraí region, and six in the Pirabeiraba region (Table 2).Dioscorea trifida is cultivated in swiddens, where it is wrapped around stakes planted by farmers.As observed by Santos [48], it is also intercropped with Zea mays L. (corn), which serves as a host, and intercropping is also performed with Colocasia esculenta (L.) Schott.(taro).

Occurrence of Dioscorea in the vegetation of shellmounds
From April 2019 to August 2021, six species of Dioscorea were recorded in the sambaquis and surrounding forests in different combinations at each site.Five are native, Dioscorea chondrocarpa, Dioscorea dodecaneura, Dioscorea laxiflora, Dioscorea olfersiana and Dioscorea scabra, and the exotic D. cayennensis (Table 3; Figs. 2, 3).
All shellmounds are surrounded by Restinga Forest, with the exception of Rua Guaíra, where there is a Dense Ombrophilous Forest (FOD).This shellmound and surrounding areas, the following tree species were identified, which according to Flora e Funga do Brasil [66] are FOD indicator species: Hieronyma alchorneoides Allemão (licurana), Nectandra membranacea (Sw.)Griseb.(canela-branca), Hirtella hebeclada Moric.ex DC. (cinzeiro) and Endlicheria paniculata (Spreng.)J.F. Macbr.(canela-frade).In the other shellmounds, tree species were recorded that, according to Falkenberg  In the shellmounds with greater intervention in their structure and vegetation from European colonization to the present, such as the exploitation of shells for the production of lime and the carrying out of archaeological excavations, Cubatão I-B, Ilha dos Espinheiros II, Lagoa Saguaçu and Morro do Ouro, we recorded several exotic food trees among Atlantic Rainforest species (Table 4).
In the vegetation associated with shellmounds, we recorded that the Dioscorea species wrap themselves around different hosts, the most frequent being We recorded yam species with aerial stems in both the warmer and colder seasons of the year.Sexual reproduction in Dioscorea species was recorded from the presence of seedlings and, less frequently, flowers and fruits, which were observed only in D. laxiflora and D. olfersiana (Fig. 3).The native D. chondrocarpa, D. laxiflora, and D. olfersiana have perennial tubers and D. scabra perennial rhizophores [47].D. dodecaneura renews its tubers annually [68].Among cultivated species in the region, only D. cayennensis and D. bulbifera have perennial tubers [44].In D. laxiflora, tubers are pyriform, the largest measuring approximately 8 cm in the widest part and with yellow pulp (Fig. 4A-C).In D. chondrocarpa, the tubers are globose to oval, measuring up to 5 cm in diameter, with yellow or purple colour, connected to a woody tuberous system (Fig. 4D-F).In D. dodecaneura, tubers are globose, measuring approximately 4 cm in diameter and with white pulp (Fig. 4I).D. scabra has elongated, fibrous, and thin rhizophores (Fig. 4K, L).In D. olfersiana, the tubers present a discoid or piriform shape and have a yellowish-white pulp.They were observed with varying sizes, between 12 and 43 cm in the widest portion (Fig. 4M-Q).In the species D. cayennensis, branched tubers with yellow colour and larger than those of native species were recorded (Fig. 4R, S).

Uses of Dioscorea species
Records of food use prevail in the literature, but there is also information on medicinal use for Dioscorea species that we recorded in wild conditions and on farms [37,43,44,[46][47][48].Dioscorea trifida was identified as the most used species within the study area, followed by D. alata in the research by Santos [48].The air yam (D. bulbifera) and the cará-de-espinho or Guineayam (D. cayennensis) are rarely used according to the research by Santos [48], a situation that remains in the studies by Veasey et al. [44], Siqueira [58] and Nascimento [59].According Santos [48], D. trifida is consumed cooked and has the tastiest tubers according to farmers.The plant is also used as a healing agent [48].According to Chu and Figueiredo-Ribeiro [46], D. trifida is used for digestive problems and asthma.The species D. bulbifera and D. alata are consumed

Folk name Shellmounds and surrounding area CUB I-A CUB I-B CUB II ECUB II ILES II EILES II LAS ELAS MA II EMA II MO EMO RGU ERGU
Native cooked [48] and used to treat skin conditions and as diuretics due to their medicinal properties [46].In Babitonga Bay, they are used in the preparation of bread [48].Tubers of D. cayennensis are consumed cooked and have medicinal uses [44].According to Barroso et al. [69], the tubers of D. dodecaneura can be eaten raw and have the flavour of almonds.In addition to being consumed boiled or roasted, D. dodecaneura is used in the production of an indigenous fermented drink called chicha [47] and in the treatment of skin conditions, rheumatism, diabetes and as a cardiotonic [46].Among the wild species registered, only D. laxiflora is considered toxic according to Chu and Figueiredo-Ribeiro [46].This species is used for female fertility and skin infections [46].Tubers of D. laxiflora, D. olfersiana and D. scabra contain diosgenin [46], a precursor of female hormones and are widely used in the pharmaceutical industry [36].Dioscorea scabra has compounds with antibacterial and antifungal activity [37].

An ancient story between Dioscorea spp. and people in Babitonga Bay
Yams are among humans' oldest foods [34] and have been recorded in archaeological sites since the Pleistocene  [35].Archaeological remains of Dioscorea have been recovered from sites in Brazil dating back to the early Holocene [70], a period that in Babitonga Bay is related to the presence of hunter-gatherers from the Umbu tradition dating from 11,000 to 8000 years cal BP [71,72] (Fig. 5).
The history between yams and people in Babitonga Bay began thousands of years ago, and even today, we find plants producing these tubers associated with places built at different times by different people and their cultures.The oldest record of Dioscorea consumption in Babitonga Bay is among the Sambaquianos in 4030 ± 40 years BP [31].Another ancient record of yam consumption among Sambaquianos was found in the south of Santa Catarina [33].In southeastern Brazil, charred archaeological fragments of Dioscorea tubers were found in shellmounds dating back to approximately six thousand years BP [23].
The shellmounds we researched date back to between 5200 and 2900 years BP (Table 1).Dating indicates that the construction of sambaquis in Babitonga Bay occurred between 6 thousand and 1000 years BP [21,73].Radiocarbon dating indicates the presence of indigenous people Jê in Babitonga Bay from 1500 years BP [74].
The Guarani left their records in archaeological sites in Babitonga Bay from 400 years BP [74] (Fig. 5), a period in which European colonizers were already present in the region [64,75,76].There are archaeological and ethnoarchaeological records that the Jê and Guarani indigenous groups also consumed Dioscorea in other regions of the state of Santa Catarina [62,63,77].The oldest record of European contact in Babitonga Bay is by Binot Palmier de Goneville in 1504 [64].According to the account of this French explorer, he found the Guarani, then called Carijós, with dozens of villages where they cultivated cassava (Manihot esculenta Crantz) and other roots and tubers, probably sweet potato, Ipomoea batatas (L) Lam., and yams (Dioscorea spp).
We recorded species of Dioscorea associated with sambaquis and swiddens in the Babitonga Bay region that maintain different relationships with people (Figs. 5,  6).Associated with the shellmounds are wild species of Dioscorea-D.chondrocarpa, D. dodecaneura, D. laxiflora, D. olfersiana and D. scabra-and the exotic D. cayennensis.In the swiddens, domesticated yams, D. alata (Asian), D. cayennensis (African), D. bulbifera (Asian and African) and D. trifida (Amazonian) [44,48,58,59].Dioscorea trifida and D. dodecaneura are among the yam species cultivated by Guarani [62,77].These and other Dioscorea species are associated with the Guarani plant pack, a set of plants and their propagules (seeds, roots, tubers and others) carried by them in their expansion to new territories, including southern Brazil, 2000 years BP [62].Dioscorea trifida is from the Amazon rainforest [78] and was domesticated by indigenous people before the European invasion.Genetic studies indicate that accessions of D. trifida from Babitonga Bay are linked to the Amazon and that their origin is related to Guarani expansion [59] (Nascimento 2013).In the Amazon region, according to Clement [78], D. dodecaneura is considered semidomesticated and a food source for indigenous peoples before European invasion, in addition to domesticated D. trifida.
Dioscorea chondrocarpa, D. dodecaneura, D. laxiflora, D. olfersiana and D. trifida began to be cultivated by farmers in Brazil through contact with indigenous peoples [46,47].By 1550, the African yam (probably D. cayennensis) was already cultivated in southeastern Brazil by colonizers and their slaves, but the indigenous people preferred the native yams that they already cultivated and because they had better flavour [79].This may also have been the scenario in Babitonga Bay.
The exotic species D. cayennensis, D. alata and D. bulbifera arrived in Brazil with colonizers from the sixteenth century onwards [43].In Babitonga Bay, the historical record of cultivation of D. alata [65] and D. bulbifera [50] was initiated by Luso-Brazilians who arrived in the region in the seventeenth century [49,76,80].Currently, they are cultivated by descendants of the Germanic colonizers who arrived in the region in the nineteenth century [44,48,58,59] (Fig. 5).
The lack of historical records on the consumption of yams native to the region by colonizers does not mean that it did not occur but may be related to the type of use that Luso-Brazilian and Germanic colonizers made of the forest in the nineteenth century.According to Saint Hilaire [65] and Rodowicz-Oświęcimsky [50], in the region, food came from swiddens with domesticated species, such as the abovementioned species, and forests were intensively cut down to build villages.At the same time, some shellmounds were dismantled to extract the shells, which lasted until the mid-twentieth century [52].These two actions resulted in the loss of vegetation and native Dioscorea species and the introduction of exotic species, as observed in some shellmounds (Table 3, 4 and Fig. 2).
Despite the strong association of native species of Dioscorea with shellmounds and diverse uses, there is no evidence or current records in the literature that the descendants of the colonizers have appropriated these species.Currently, descendants cultivate domesticated yams, and forest areas are replaced by different crops.Wild yam is a plant with great potential for use and is apparently not known.An important aspect to be considered in possible future uses of the vegetation Considering that the exotic African and Asian species of yam arrived in Brazil only after colonization in the sixteenth century, we can infer that the Sambaquianos, Jê and Guarani consumed the native species of Dioscorea, and among these, the native species that currently occur are associated with shellmounds and D. trifida is associated with swiddens.

Yams in a domesticated landscape
The Babitonga Bay landscape is home to approximately 170 sambaquis [73] that are integrated into the Restinga forests and mangroves.Among the sambaquis researched, the exception is the Rua Guaíra, which was built on the slope of a small hill and is currently associated with the Dense Ombrophilous Forest.However, although they are currently integrated into the abovementioned ecosystems, they contain plant species from other regions of Brazil and even other countries.For example, in some shellmounds, we recorded exotic food plants related to European colonization (Table 4).In the case of Persea americana (avocado) and Psidium guajava (guava), which are not native to the region, they were probably already cultivated in Brazil before colonization [81,82].In the vegetation on and around the sambaquis, we recorded six species of Dioscorea, five native and the exotic D. cayennensis, African yam.The occurrence of plants of different origins indicates human influence at different times that have moulded the current landscape.
The expressive presence of sambaquis in the current landscape refers to an intense interaction between their builders and the environment.Archaeobotanical studies in shellmounds indicate that Sambaquianos mainly uses Restinga plants [23], including in Babitonga Bay [19].However, Archaeobotany is a recent area of research in Brazil [83], and this is reflected in the small collection of archaeological food plant remains identified in shellmounds.Most of the archaeobotanical remains identified in sambaquis are from tree species from charcoal [19,23,84].The first use mentioned is as fuel, but it is clear that many of the identified species produce edible fruits.The Myrtaceae family, which is very diverse in Restinga and well represented in archaeological remains [23], produces fruits that are highly appreciated by people.Examples are species of the genera Psidium and Eugenia [23], which we recorded to be associated with the sambaquis studied as Psidium cattleyanum (araçá) and Eugenia astringens Cambess (jabuticaba-da-praia).We recorded other plant species from Restinga associated with shellmounds, previously identified archaeological remains in Babitonga Bay.Trees such as Andira fraxinifolia and palm Syagrus romanzoffiana were identified by Melo Junior et al. [19] and Oliveira and Melo Junior [84].Of the remains identified as Araceae by Wesolowski et al. [31] and Philodendron [85], we recorded Monstera adansoni and Philodendron appendiculatum in the current vegetation.Food plants such as Dioscorea spp.also identified by Wesolowski et al. [31] we registered in shellmounds D. chondrocarpa, D. dodecaneura, D. laxiflora and D. olfersiana, and medicinal plants D. scabra.All of these plants and countless others, with different uses for people, are in wild conditions and do not depend on human action to reproduce, persist and perpetuate in the environment.
Direct identification of plant consumption among Sambaquianos was carried out through the extraction of remains in dental calculi by Wesolowski [30] and Boyadjian [32] and by stable isotopes Pezo-Lanfranco et al. [86] and Toso et al. [87].Among the remains, starch granules of Dioscorea sp. were identified, others suggestive and similar to Ipomoea batatas (sweet potato), Zea mays (corn) and Araucaria angustifolia [31,33].According to these authors, other remains, including starch granules and phytoliths, were identified as Marantaceae, Araceae and Poaceae.
Given the archaeobotanical research cited above, there is no doubt that the Sambaquianos used and consumed plants and that the consumption of carbohydrates was significant, as noted by Wesolowski [30] and Pezo-Lanfranco et al. [86].Based on this reduced archaeobotanical data set of evidence for plant consumption, Pezo-Lafranco et al. [86] in their research and in review articles Scheel-Ybert and Boyadjian [29] and Scheel-Ybert et al. [88] suggest a mixed economy among Sambaquianos with the cultivation of domesticated plants.
Although there has been a record of plant cultivation in Brazil since 12 thousand years BP [82], it is still premature to confirm horticulture and the cultivation of domesticated plants among shellmound builders.Even with the spread of horticulture and agriculture, indigenous groups choose not to do so.In the Neotropics, there are several systems for obtaining food plants that are independent of cultivation and domestication [82].In the lowlands of South America, of the 6261 plant species used, only 0.7% are completely domesticated, and gathering represents 98.6% of the way to obtain useful plants, among which 53% are trees [82].Edible tubers of Dioscorea species can be collected and managed in the forest and cultivated [36,40,44,46,47,89].For example, the indigenous Nukak people in the Amazon form wild orchards where they promote some species over others, thus increasing the productivity of the forest [90].
There are wild species of Dioscorea [43,46,47], Ipomoea [91,92] and Poaceae [93] that are used in food and that could simply be gathered and managed.It is not always easy to distinguish between remains, such as starch grains and phytoliths, from wild and domesticated plants [93,94].
Currently, native species of Dioscorea recorded in shellmounds and surrounding vegetation perform sexual reproduction and do not depend on human action for their perpetuation in the environment.However, this does not rule out human influence in the past.Interactions between people and forests have occurred for thousands of years and can be perceived through patches of useful plants near archaeological sites [4][5][6][7][8][9][10][11][12][13][14].The current vegetation that we have recorded in the shellmounds in Babitonga Bay developed on mounds built by humans.Sambaquis are anthropogenic structures [25] and intentionally built [24], with high fertility similar to that of Amazonian Dark Earth (Terra Preta de Índio) in the Amazon [26] and may harbour vegetation different from that found in nonanthropic soils.
In sambaquis and swiddens, we record species of Dioscorea that are food and medicinal, according to the literature [37,43,44,[46][47][48].The yams of shellmounds, Dioscorea scabra, a medicinal plant [37], is endemic to Brazil [95] and the most frequent Dioscorea in the state [47].Dioscorea olfersiana is endemic to the Atlantic Forest, with sparse occurrence in Santa Catarina state [95] and cultivated in other regions of Brazil, as are D. chondrocarpa and D. laxiflora [46,47].Santa Catarina state appears to be the southern limit in the Atlantic Forest for D. chondrocarpa and D. olfersiana [95].
The five native species of Dioscorea that we recorded in the vegetation associated with shellmounds (Figs. 2, 3, 4; Table 3) are on the coastal plain, a few meters above sea level and associated with the Restinga Forest and Dense Lowland Rainforest.However, according to Pedralli [47] and Couto and Fraga [95], these native species have been recorded preferably in the hillside forests of the Atlantic Forest.In addition to being outside the preferred environment, we registered different combinations of Dioscorea among shellmounds in the same type of phytophysiognomy.This species composition may be related to the preference and manipulation of human groups in the past.A scenario similar to that proposed by Cruz et al. [20] when analysing the current vegetation of the Atlantic Forest in the state of Santa Catarina close to archaeological sites suggests a process of cultural niche construction.
The species D. dodecaneura before our research had only four records in SpeciesLink [96] and only one in Reflora [97] for the state of Santa Catarina.According to Pedralli [47], it is a rare species in Santa Catarina state and is possibly threatened with extinction, but in other regions of Brazil, it is cultivated.Considering its rarity, its preference for hillside forests in other regions of this biome [96,97], and its occurrence restricted to the Cubatão I and Cubatão II sambaquis may indicate mediation by the Guarani indigenous peoples thousands of years ago in their expansion of Amazonia, as indicated by Noelli [62] and Pereira et al. [77].According to Oliveira et al. [98], D. dodecaneura occurs in the vegetation associated with the archaeological site they studied in the southeastern region of Brazil and is currently used by the local community.
We recorded tubers of D. dodecaneura and D. laxiflora with sizes similar to those described for these species in wild conditions according to Barroso et al. [69], that is, they come from seeds that weigh a maximum of 200 g.In cultivation, through vegetative propagation, tubers of both species can reach up to 2.0 kg [47].According to Onwueme [99], plants originating from tuber fragments have faster and more vigorous growth than those originating from seeds.Cultivation promotes an increase in yams through nutritional enhancement and better light conditions [36,38] but also through the selection of phenotypes of interest to humans [9,14].The vegetative propagation of small fragments left in food preparation areas is one way to increase the density of Dioscorea plants in a location [40].Shellmounds as funerary monuments built over thousands of years [24], where large parties were held during the burial of the dead [27].The recurrent preparation and consumption of yams near these sites could have formed a concentration of these plants by vegetative reproduction.Charred fragments of Dioscorea tubers were recovered from shellmounds in southeastern Brazil by Scheel-Ybert [23].
An interesting characteristic that we observed among the Dioscorea species that we recorded in shellmounds is the perenniality of the tubers.The perennial nature of Dioscorea tubers is common in tropical forests [36].The perenniality of the tubers associated with the formation of Dioscorea patches guarantees a prolonged source of food for local people, as reported by Yasuoka [40] and Scarcelli et al. [89] in Africa, by Head et al. [100], Atchison and Head [101,102] in Australia, and Ferreira et al. [103] in Brazil.Dioscorea patches are gardens in the territory, ancestral places that are not routinely visited, they are in the memory of people, whose practices involving the care, gathering and replanting of tubers transform the landscape [100][101][102].Among the six species we recorded associated with shellmounds and forests, five have perennial tubers or rhizophores.The exception is D. dodecaneura, which renews its tubers annually and in a similar way to D. trifida, according to Couto et al. [68].In this sense, it can be proposed that the Sambaquianos and the other people who succeeded them were able to manage yams in the forests, which corroborates the statement by Toso et al. [87] that the Sambaquianos consumed plants harvested from the local forests.However, considering that in the forests of the region, we have recorded wild species that are currently cultivated in other regions of Brazil, the cultivation of yams among the Sambaquianos cannot be ruled out.
Among the native species associated with shellmounds, only D. laxiflora is cited in the literature as toxic [46,104].D. laxiflora has steroidal sapogenins, most of which are diosgenin [46,69].According to these authors, together with other secondary compounds such as toxic alkaloids, sapogenins act in the defence against herbivory.At least the majority of the toxins in Dioscorea appear to belong to one of three main categories: alkaloids, tannins and saponins [36].For Corrêa [43] and Chu and Figueiredo-Ribeiro [46], D. laxiflora is edible, but not cultivated, is gathered and managed.However, for Pedralli [47], D. laxiflora is cultivated and used by small farmers in the state of Minas Gerais, Brazil.According to Corrêa [43], the tuber of D. laxiflora, known as caratinga-brava or cará-de-sapo, needs to go through a long cooking process to become edible.According to Coursey [36] and Lebot [38], there are traditional ways to remove toxicity from tubers before consumption, such as immersion in water and ash for a few days.The toxicity of a plant does not prevent its use.D. laxiflora flour of the cooked tuber is mixed with corn flour to produce bread [43].The folk name also indicates possible toxicity, similar to what is recorded by Peroni et al. [105] in Manihot esculenta (cassava), where the term bitter or brava (mandioca-brava) in Portuguese refers to the variety that has the highest concentration of toxin.However, in addition to steroidal sapogenins, D. laxiflora may have other toxic secondary compounds, and therefore, further studies are necessary.
The tubers of many species of Dioscorea are highly toxic and may be used deliberately as sources of poison for hunting, fishing, sanitary or criminal purposes [36] and may also be used for D. laxiflora.Indigenous people use Dioscorea species poison in fishing [106].The main toxic content is dioscorine, an alkaloid present in most Dioscorea species [104,107].In the domestication process, the physicochemical characteristics of the tuber are the main characteristics that are selected, and the reduction of toxic compounds, for example, becomes a difference between the tubers of wild and domesticated plants [38,108].An assessment of the level of toxicity between cultivated plants and the wild conditions of D. laxiflora could determine its degree of domestication in this regard.
Just as there are Dioscorea species associated with the niche built by shellmound builders, there are domesticated yam species in the region that depend on the niches built by farmers (Fig. 7), cultivated landscape units [109,110] associated with a domesticated landscape containing species preferred by humans [2].According to Santos [48], in their swiddens, local farmers reproduce the conditions and means necessary for the vegetative reproduction of the domesticated Dioscorea species D. alata, D. bulbifera, D. cayennensis and D. trifida.In swiddens, domesticated yams produce tubers from 1.5 kg to 10 kg [44].These plants are linked to the memory of colonizing families and are considered a cultural asset in the Babitonga Bay region [111].Although most swiddens are not directly related to the estuary and shellmounds, there is continuity between landscape units.The occurrence of the species D. cayennensis associated with three shellmounds is evidence of this continuity.However, the record of only adult and isolated individuals, without evidence of sexual reproduction, is an example of human dependence on reproduction, as also observed by Veasey et al. [44] in secondary forests.The exotic D. cayennensis is African and domesticated [42], and its presence in shellmounds in Babitonga Bay is associated with the old swiddens of colonizers that, according to Cunha [80], had dozens of enslaved Africans from the seventeenth century onwards.
In cultivation, yams are wrapped around stakes placed by farmers or around hosts such as Zea mays (corn) or around trees in agroforestry systems [48].Dioscorea in the shellmound vegetation and the surrounding forest wrap mainly around hosts, such as small trees, shrubs, herbs and other vines.According to Campanello et al. [112], climbers prefer to use plants with smaller stems first to reach the tree canopy.
Given the presented chronology and the relationship between indigenous peoples, colonizers, and native and exotic species of Dioscorea (Figs. 5,6,7), it is possible to infer that the native yams that currently occur associated with shellmounds are potentially species that the Sambaquianos consumed and whose starch grains were isolated by Wesolowski [30] in Morro do Ouro shellmound.However, given the wide variation in shape and size of starch granules within the same wild species [69,113] and the small number of granules isolated by Wesolowski [30], it is difficult to determine the exact species and whether it is wild or domesticated.The size and shape of the granules presented in the abovementioned study could belong to the species that we recorded and even to others that we did not find but that could have occurred in the past in the region.Currently, the native species recorded in shellmounds and surrounding forests are in wild conditions.However, this does not rule out human influence in the past.According to Scheel-Ybert [23], considering the macroremains of plants recovered in sambaquis and the diversity of food plants in the Restinga, such as fruits, seeds, roots and tubers, it would indicate that the gathering and management was carried out by Sambaquianos, but they would be outside an agricultural context.Boyadjian et al. [33] suggest an association between collection and cultivation among the Sambaquianos who built the Jabuticabeira II shellmound, south of Santa Catarina, but this hypothesis would still need to be investigated through continued studies and other indicators.
Considering that two studies were carried out with the extraction of microremains of food plants in dental calculi among Sambaquianos [30,32] and that the registered plants have wild relatives, new archaeobotanical research in sambaquis is essential to reach specific taxa and, if applicable, confirm horticulture among the Sambaquianos.

Conclusions
Shellmounds and associated forests, and in swiddens, are two contiguous landscape units that have been shaped over thousands of years and are part of a mosaic of cultural legacies.
Native and wild Dioscorea occur on shellmounds and exotic and domesticated yams occur in swiddens.They are food and medicinal species of Dioscorea.
Considering that the exotic African and Asian species of yam arrived in Brazil only after colonization in the sixteenth century, we can infer that the Sambaquianos, Jê and Guarani consumed the native species of Dioscorea associated with shellmounds, D. chondrocarpa, D. dodecaneura, D. laxiflora, D. olfersiana and D. scabra, and D. trifida associated with swiddens.
The restricted occurrence of D. dodecaneura-a semidomesticated species in the Amazon Rainforest-in the Cubatão I and Cubatão II shellmounds deserves further investigation, especially regarding its distribution in the region.
Greater investment is necessary in research into archaeological remains of plants in sambaquis.Of the remains identified thus far, doubts still remain about the taxa and whether they truly are plants that would necessarily need to be cultivated or could simply be gathered and managed in the forests.
There is a lack of studies on native Dioscorea species, mainly on their life history and use.Most studies are about taxonomy.Genetic studies conducted within and among Dioscorea populations that occur in shellmounds and surrounding vegetation would contribute to the understanding of human manipulations over time.In addition, ethnobotanical studies with yam producers in the region and in communities close to the shellmounds would be complementary and help better understand possible uses of native Dioscorea species in wild conditions.

13 Fig. 1
Fig. 1 Shellmounds in Babitonga Bay, Joinville, Santa Catarina state, selected for the study.A Map with location of the shellmounds around Babitonga Bay; B Ilha dos Espinheiros II; C Cubatão I; D Rua Guaíra; E Cubatão II; F Morro do Amaral II; G Morro do Ouro; H Lagoa Saguaçu

Fig. 2 Fig. 3
Fig. 2 Graph showing the distribution of Dioscorea species on the shellmounds and along the transects in the surrounding vegetation

FamilyFig. 4 13 Fig. 4 (
Fig. 4 Tuberized subterranean organs of Dioscorea species associated with the surveyed shellmounds, Joinville-Santa Catarina state.A-C tubers of D. laxiflora collected in the surrounding vegetation of Ilha dos Espinheiros II; D-F tubers of D. chondrocarpa recorded in the surrounding vegetation of Ilha dos Espinheiros II; G young tuber of D. chondrocarpa in the vegetation around Morro do Amaral II; H, J detail of variegated leaves and purple abaxial face of D. dodecaneura on Cubatão I-A; I tuber of D. dodecaneura on Cubatão II; K, L rhizophores of D. scabra in the vegetation around Rua Guaíra; M-P tubers of D. olfersiana recorded in the vegetation around Ilha dos Espinheiros II; Q tubers of D. olfersiana recorded in the vegetation around Cubatão II; R, S tubers of D. cayennensis recorded in the vegetation around Ilha dos Espinheiros II and Cubatão I-B, respectively (See figure on next page.)

Fig. 5
Fig. 5 Timeline with recorded Dioscorea species in the study area and precolonial and colonial human groups

Fig. 7
Fig. 7 Representation of landscape units where Dioscorea species were recorded in the study area: shellmounds and associated vegetation and swiddens.1: rods with D. alata, D. bulbifera and D. trifida in swiddens; 2: D. cayennensis inter shellmound and swiddens; 3: D. chondrocarpa, D. dodecaneura, D. laxiflora, D. olfersiana and D. scabra in shellmounds Dioscorea species used in the precolonial, colonial, and current periods was carried out with Google Scholar.The keywords used were precolonial history of Joinville and São Francisco do Sul; Dioscorea or yam in Santa Catarina; colonization of Joinville and São Francisco do Sul; and indigenous ethnobotany in Santa Catarina.Additionally, the research relied on literature borrowed from local historians.
in Morro do Ouro shellmound at 30 m beyond the road; in Ilha dos Espinheiros II at 20 m beyond a parking lot; and in Cubatão II beyond a 10-m-wide stream.We did not search in the forest around the sambaqui Cubatão I.The survey of

Table 3
Dioscorea species recorded in the vegetation on the shellmounds and surroundings in the study area CUB I-A portion of Cubatão I shellmound with forest, CUB I-B portion of Cubatão I shellmound with grasses and sparse tree vegetation.CUB II Cubatão II shellmound, ECUBII Cubatão II surrounding area, ILES II Ilha dos Espinheiros II shellmound, EILES II Ilha dos Espinheiros II surrounding area, LAS Lagoa Saguaçu shellmound, ELAS Lagoa Saguaçu surrounding area, MA II Morro do Amaral II shellmound, EMAII Morro do Amaral II surrounding area, MO Morro do Ouro shellmound, RGU Rua Guaíra shellmound, ERGU Rua Guaíra surrounding area.1:this Dioscorea sp.Present; 0: this Dioscorea sp.Absent

Table 4
Exotic food trees registered on the shellmounds discussed in this study CUB I-A portion of Cubatão I with forest, CUB I-B portion of Cubatão I with grasses and sparse trees, CUB II Cubatão II, ILES II Ilha dos Espinheiros II, LAS Lagoa Saguaçu, MA II Morro do Amaral II, MO Morro do Ouro, RGU Rua Guaíra.1: this tree sp.present; 0: this tree sp.absent area da Silva Souza et al.Journal of Ethnobiology and Ethnomedicine (2024) 20:13CAAE Certificate of presentation of ethical review ISE International Society of Ethnobiology IPHAN Institute of National Historical and Artistic Heritage SAMA Secretary of Agriculture and Environment of Joinville UGA Environmental management unit FUMDES State Fund to Support the Maintenance and Development of University Education in Santa Catarina SC Santa Catarina state CNPQ National Council for Scientific and Technological Development LAC Radiocarbon Laboratory of the Universidade Federal Fluminense, Rio de Janeiro, Brazil